1. Field of the Invention
The invention relates to spray forming technology. In particular, the invention relates to a spray forming device and process to form ring geometries using inner diameter (ID) spraying.
2. Description of Related Art
A clean melting system for use in spray forming is disclosed in U.S. Pat. No. 5,160,532, the entire contents of which are incorporated by reference. The system disclosed in U.S. Pat. No. 5,160,532 uses a combination of an electroslag remelt furnace (ESR) and a cold induction guide (CIG).
Ring type structures have been previously made using several diverse methods. These methods include centrifugal casting, centrifugal atomization and spray forming. However, these methods have limitations regarding the number of different geometries and structures that can be accurately and properly formed.
Centrifugal casting generally involves the introduction of liquid metal into a rotating cylindrical mold. The rotation of the mold is at a speed to permit centrifugal acceleration to force the introduced liquid metal to outer diameter portions of the mold. The liquid metal can then solidify at those outer diameter portions of the mold. However, centrifugal casting is not suitable for use with articles that have at least one of intricate and complicated geometries, as for example, a tapered ring or a ring with varying cross-sectional area. Further, centrifugal casting is limited in use due to solidification rates of the associated liquid metal alloys, which would reduce the applicability of this method.
Centrifugal atomization involves generating an atomized liquid metal stream. A liquid metal stream is caused to be directed or fall on a rapidly rotating surface. The rotating surface atomizes the liquid metal stream. This also causes the atomized liquid metal stream to fall or be directed in a generally radially outward direction with a radially outward velocity. The generated atomized liquid metal stream cools somewhat over its movement. It is then collected on an inner diameter of a collector to form an article. However, centrifugal atomization is not suitable for spray forming articles that have various and complicated inner geometries.
A spray forming process uses gas atomization to form a spray of liquid metal droplets. The spray forming process directs the liquid metal spray onto a solid body. This solidifies the liquid metal spray to form a billet or billet preform. Spray forming has been used to manufacture cylindrical shapes, which can be either solid or hollow. Ring shapes and geometries have been sprayed successfully using an outer diameter (OD) spray forming. However, this type of spray forming process is not adequate for inner diameter (ID) spraying because of the complexities and difficulties in placing spray forming components inside an article to be formed, so as to spray form an inner diameter of an article.
Further, various problems have been associated with OD spraying, where these problems have prevented an acceptable end product from being formed. Problems, such as but not limited to, an increased porosity at the ID and a low yield, have prevented OD spraying from achieving an acceptable and desirable end product.